Self powered wireless sensor for indoor environment monitoring
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“Self Powered Wireless Sensor For Indoor Environment Monitoring”
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Transcript of Self powered wireless sensor for indoor environment monitoring
“Self Powered Wireless Sensor
For
Indoor Environment Monitoring”
Contents
Page 2
About the Authors
Introduction
Basic system design
Piezoelectric Bimorph Generator
Power Conditioning Circuit
Sensor & Radio Hardware
Packaging
Results
Advantages & Disadvantages
Conclusion
About the Authors of Ongoing Research
Page 3
The authors of the paper are
Eli S. Leland, Elaine M. Lai, Paul K. Wright(Department of Mechanical
Engineering, University of California, Berkeley)
They are all researching in the field of wireless sensors.
Introduction
Page 4
Energy crises in California.
Need of sensor for smart environment.
Choosing the power source.
Why not Solar?
Basic System Design
Page 5
Page 5
Piezoelectric Bimorph Generator
Power Conditioning circuitry
Sensor Hardware Wireless Radio
AC Current
DC Current
Temp. Reading
Piezoelectric Bimorph Generator
It consists of a metal sandwiched by two layers of piezoelectric material.
It has a proof mass attached on the one end and its other end clamped to the
vibration source.
Page 6
Schematic Diagram Actual Setup
Page 6
Power Conditioning Circuit
Piezoelectric Bimorph produces AC Voltage which is not sound for the devices
like wireless radio etc. so this conditioning circuit converts AC to DC and feed it
to the next level.
Actually generator does not provide sufficient energy to operate the wireless
sensor so we need to store the energy produced from the generator so that
when we have sufficient energy we can feed it to the sensor.
Page 7
Schematic Diagram
Cont…
Page 8
Actual Prototype
Sensor & Radio Hardware
This hardware consist of a temperature sensor which is a thermistor.
A wireless radio Mica2Dot was chosen as the wireless platform for this project.
Page 9
Mica2Dot Wireless sensor network
Packaging
Page 10
Package Prototype
Cont…
Page 11
Assembled Prototype
Results
Page 12
Capacitor Discharge
Cont…
Once fully charged to its threshold value (5 V) the capacitor starts to discharge
and till it discharge to its lower threshold (3.5 V) it provides 3.3VDC to the circuit
for 816 ms.
The sensor is programmed to send temperature readings every 10 ms.
It sends 2 readings from that time window of 816 ms because the sensor takes
800 ms to initialize and sends the readings in next 16 ms.
Power transfered through the capacitors was 108mW and power input to the
sensor and radio hardware was 45mW. The overall efficiency of the power
transfer was 42%.
Page 13
Disadvantages
No need for external power source.
No cables attached so easy to maintain.
Charged by daily routine activities like walking.
Advantages
In the experiment results show that 50 minutes of the continuous traffic is
required to provide the temperature readings. So it is quite disappointing
because of this much less power generation.
The efficiency of power conditioning circuit is only 42%.
Page 14
Conclusion:
This device verifies the feasibility of powering such a device in a real-world
deployment situation, in this case a wooden staircase.
A number of areas for the improvement are identified in this project like using a
sensor which takes very less initializing time, and a capacitor with lower leakage
characteristics.
Instead of a wooden staircase we can use a ventilation duct for providing more
vibrations.
Page 15
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